PSI - Issue 44

Gaspar Auad et al. / Procedia Structural Integrity 44 (2023) 1474–1481 Gaspar Auad / Structural Integrity Procedia 00 (2022) 000–000

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Fig. 5. (a) Base-isolated structure. (b) Frame elevation in the XZ-plane. (Modified from Auad and Almazán (2021)).

In Fig. 6, a comparison of the dynamic response of the building isolated with the two studied isolation systems is presented. The building was subjected to the three components of the El Centro Array #4 (Imperial Valley-06 Earthquake, 1979). The trajectory of the base for both isolation systems is plotted in Fig. 6((a), and (b)). Note that the changes in the curvature of the isolation systems formed by variable curvature isolators decrease the maximum lateral displacement. This reduction in the maximum base displacement demand affects the maximum force developed in the isolation system. The normalized hysteretic loops of the isolation system are shown in Fig 6((c), and (d)) in the x and y-directions, respectively. The base shear in both horizontal directions (i.e., " and $ ) are normalized by the total vertical reaction ' . The initial radius E of the devices normalizes the lateral displacement in both directions (i.e., " and $ ). The increment of the stiffness at large base displacements of elliptical frictional isolators can reduce the dramatic rise in the base shear produced by internal impact by reducing its magnitude or avoiding the impact occurrence. One of the adverse effects of internal lateral impacts is an intense increase in the deformation of the superstructure. In Fig 6((e), and (f)), the inter-story drift response of the first and third stories in the y-direction (the critical direction) is shown. The maximum drift demand is significantly reduced when variable curvature isolators form the isolation system.

0.1 0.2

-0.3 -0.2 -0.1 0

3rd. story drift y-direction (%)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 time (sec)

(e)

(c)

(a)

0.1 0.2

-0.3 -0.2 -0.1 0

first. story drift y-direction (%)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 time (sec)

(f)

(d)

(b)

Fig. 6. Comparative dynamic response of a structure equipped with frictional isolators. (a) Trajectory of the base using FPS bearings; (b) Trajectory of the base using elliptical-shaped bearings; (c) Normalized hysteretic loops in the x-direction; (d) Normalized hysteretic loops in the y-direction; (e) Third story drift in the y-direction; (f) First story drift in the y-direction.